After I compared the performance of Windows 7 with that of Windows Vista , a lot of readers expressed interest in seeing a comparison with the decade-old, but still popular, Windows XP. So I decided to see how each of the three operating systems compared to each other in several crucial categories. Frankly, the results were a bit surprising. While they aren't a knockout blow for Windows 7, they do show that, by some measures, XP outperforms Windows 7 on legacy hardware.

To start, I did a clean install of each OS on a 1.73-GHz Toshiba Satellite M45-S269 laptop with 1GB RAM and a 100GB hard drive. Because upgrading from XP will be of interest to businesses as well individuals, I chose to install Windows XP Professional, and stuck with the Professional edition for Vista and 7. I used 32-bit versions, since most XP installations are of that variety. For each OS version, I performed a clean installation.

I then installed Microsoft Office 2007 Ultimate , Windows Live Essentials (Mail, Movie Maker , Photo Gallery , Messenger), and Picasa 3.5 , since testing a PC with no programs installed wouldn't tell much about real-world performance. Then I ran a series of tests to determine the PC's start-up and shutdown times in each OS, as well as its performance on a series of benchmark tests. I ran each test at least three times and averaged the results.

Start-up and ShutdownThe results from these two most basic tests were somewhat surprising. For startup comparison, I pressed the power button and stopped the timer when the desktop and all interface elements appeared and the Start menu became operational. Windows XP actually started up fastest, but keep in mind that my test machine was built in the XP days; new machines will be more tuned for quick start-up in Windows 7, possibly very quick start-up. But for the purposes of this story, testing on one of those machines would be pointless—this story's about the experience those who are upgrading can expect. For most people, that means an older machine.

Windows XP

Windows Vista

Windows 7

Start-up time (in minutes:seconds)

0:49

1:07

1:03

Shutdown time (in seconds)

17

12.5

11.5

Picasa video Encoding (in minutes:seconds)

5:36

6:02

5:41

Geekbench (higher is better)

1,241

1,248

1,260

SunSpider (in milliseconds, lower is better)

3,170

2,647

1,828

PCMark05 (higher is better)

1,868

1,731

1,823

* Green is best, red is worst.

Windows 7 evened the score when it came to shutdown, however, besting XP by an impressive 5.5 seconds, or 32 percent. As in my previous testing, Windows 7 surpasses Vista in both start-up and shutdown time. One of the major criticisms of XP performance has been the long "Windows is shutting down" time, and my testing bears this out. Even Vista shut down faster than XP did. Of course, startup speed is far more important to most users—so far, XP is in the lead.